1661237281 has 16 divisors (see below), whose sum is σ = 1851030720. Its totient is φ = 1478243520.

The previous prime is 1661237239. The next prime is 1661237287. The reversal of 1661237281 is 1827321661.

It is a cyclic number.

It is not a de Polignac number, because 1661237281 - 2⁹ = 1661236769 is a prime.

It is a super-2 number, since 2×1661237281² = 5519418607568545922, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 1661237281.

It is not an unprimeable number, because it can be changed into a prime (1661237287) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 91171 + ... + 107863.

It is an arithmetic number, because the mean of its divisors is an integer number (115689420).

Almost surely, 2^1661237281 is an apocalyptic number.

1661237281 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1661237281 is a deficient number, since it is larger than the sum of its proper divisors (189793439).

1661237281 is a wasteful number, since it uses less digits than its factorization.

1661237281 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16896.

The product of its digits is 24192, while the sum is 37.

The square root of 1661237281 is about 40758.2786805331. The cubic root of 1661237281 is about 1184.3422512472.

The spelling of 1661237281 in words is "one billion, six hundred sixty-one million, two hundred thirty-seven thousand, two hundred eighty-one".